1. Field of the Invention
The present invention relates to a cooling transport device for use in an image forming apparatus such as a copying machine or a facsimile apparatus to cool and transport a recording medium on which an unfixed toner image is thermally fused and fixed, and the image forming apparatus using the cooling transport device.
2. Description of the Related Art
In conventional copying machines or printers of electrophotography, a thermal fixing method has been well known in which the unfixed toner image on the recording medium is thermally fused and fixed. However, if the fixing is sped up or repeated continuously, the toner is less hardened because the recording medium after fixing is cooled insufficiently, whereby it was apprehended that the sheets might adhere to each other due to less hardened toner between discharged recording mediums. Moreover, the charged toner was affected by the exhaust heat from the recording medium caused by transporting the recording medium after fixing at the time of printing on both sides, whereby it was apprehended that the image abnormality such as uneven density might occur.
In order to solve those problems, the cooling transport device that compulsorily cools the recording medium immediately after fixing is well known (e.g., refer to JP-A-2003-233227).
In the document JP-A-2003-233227, a cooling method is proposed in which a pair of rotation bodies having a heat absorbing roll 101 with an elastic layer 101a and a roll 102 composed of a heat pipe are pressed against each other to form a nip area, and to tenaciously transport and cool the recording medium 103 immediately after fixing through this nip area, as shown in FIG. 8A.
Additionally, in this patent document, another cooling method was proposed in which a transporting belt 106 having good thermal conductivity is bridged between a roll 104 composed of a heat pipe and another roll 105, and the heat absorbing roll 101 with the elastic layer 101a is opposed to the transporting belt 106 to form a wide nip area, and transport and cool the recording medium 103 after fixing on the transporting belt 106, as shown in FIG. 8B.
However, since it is difficult to take a wide nip area in the type of transporting the recording medium between one pair of rotation bodies, the effect of cooling the recording medium was insufficient. On the other hand, in the type of using the transporting belt, though the wide nip area could be taken, the recording medium was cooled owing to the cooling effect of the transporting belt itself, in which there was a problem that the cooling effect in the nip area was impaired because the coolness of the transporting belt was lost before reaching the nip area.